The present invention relates to an image recording apparatus such as a copying machine, more particularly to an improvement on a mechanism for varying copying magnification for forming a different copying magnification image corresponding to an original on a photosensitive recording medium.
In general, on the recording apparatus, a mechanism for varying copying magnification is employed to form a different copying magnification image on a photosensitive recording medium. A lens unit is moved to and positioned at a position corresponding to copying magnification by the mechanism for varying copying magnification.
In one conventional image recording apparatus, the mechanism for varying copying magnification comprises a position setting pin provided on a lens unit and actuated by a driving means such as a solenoid, a plurality of position setting holes vertically arranged on a frame of the copying machine for fixing the lens unit at the positions corresponding to the copy magnifications.
With this structure, the lens unit is moved vertically by a driving means such as a stepper motor in accordance with the changed copying magnification, then when the position setting pin reaches a position corresponding to a prescribed position setting hole, the position setting pin is actuated toward the frame and inserted into the position setting hole by the solenoid, to thereby fix the lens unit to the frame.
However, since the conventional copying machine, having the mechanism for varying copying magnification, has a safety mechanism for cutting off a power supply when an error such as the opening of a cover for covering an original occurs during copying operation, if an error occurs during movement of the lens unit, the lens unit is stopped before the lens unit reaches the position setting hole. That is, the position setting pin is not inserted into the position setting hole and the lens unit is stopped in a precarious condition. As a result, the lens unit may move by itself with a shock or the like and, in some cases, the lens unit may drop to a lowermost position and be broken.
Further, when the power supply the overall machine is cut off due to a power failure pulled plug or switching off, the same problem occurs.